The wreckage exhibits damage patterns consistent with severe impact with the terrain. The main-rotor blades show damage characteristic of a helicopter rotor system turning at low-rotor rpm and striking the terrain. Furthermore, the damage and distress to the IFWU show that the unit had malfunctioned: the damage is not characteristic of impact damage. It is concluded, therefore, that the main rotor was not being driven at impact. The helicopter was hovering in calm air about 165feet above ground level, at a density altitude of more than 6000feet. Out-of-ground-effect manoeuvring at this density altitude at high gross weight places a large torque loading on the main-rotor transmission and driving components. At this high power setting and blade pitch angle, the loss of drive resulted in rapid decay of the main-rotor rpm, and the proximity to the ground left little room for recovery. The pilot could not regain the rpm and was unable to prevent the helicopter from descending rapidly when the lift being generated by the rotor blades was no longer sufficient to sustain flight. Jettisoning the load lightened the helicopter, allowing it to climb momentarily; it then continued to descend and struck the terrain. It was assessed that the fuel remaining at impact was sufficient for 15minutes of flight before requiring refuelling. The engine was running on the ground after impact. Because the engine was capable of producing full power during the test cell examination, vibration levels were acceptable, and the engine was operating on the ground after impact, it is concluded that the engine did not lose power during flight. The IFWU showed signs of distress related to the RHL external load type of operation, which imposed a high number of loading cycles, in the order of 30perhour. This high cycle rate accelerated the wear on the load-bearing surfaces resulting from spalling and abrasive wear. The scheduled TBO for the Lama's IFWU is not based on the number of operating cycles. Eurocopter considers time-in-service the sole parameter for determining TBO. The IFWU was subjected to a high number of loading cycles and contamination; accordingly, the IFWU, with only 1090hours since overhaul, malfunctioned before its TBO. A review of the technical records for the accident helicopter revealed that the 800-hour inspection of the IFWU was not accomplished; therefore knowledge of its structural integrity was compromised. Compliance with this inspection may reduce the risk of failure by affording an opportunity to identify anomalies and consequently return the IFWU to a Eurocopter- approved repair facility for overhaul and to clean the unit of contamination before return to service. During the freewheeling condition and repeated cyclic loading of the IFWU, the debris generated by the wear processes acted as an abrasive, causing accelerated wear of the cage/retainer, ramps, ring, and rollers. This metal debris was trapped within the assembly because of its design, contaminating the IFWU. Rapid descent and flare may cause the main rotor to accelerate, and the IFWU may disengage (or freewheel) and then re-engage. Although the composite main-rotor blades are more aerodynamically efficient than the original Eurocopter metal blades, both sets of blades can enter autorotation. The degree to which this occurs depends on flight profile, pitch angle, density altitude, and aircraft gross weight. The manner in which the helicopter was being operated is believed to have contributed to freewheeling. The IFWU would have been subjected to more frequent and severe re-engagements, accelerating the wear. The approved RFM supplement for the composite main-rotor blades supplemental type certificate was not incorporated in the accident helicopter's RFM. Further, the pitch indicator gauge was not placarded in accordance with this approved supplement. The operator may not have respected the limitation associated with the LOM blade installation. This situation may have contributed to overloading the IFWU.Analysis The wreckage exhibits damage patterns consistent with severe impact with the terrain. The main-rotor blades show damage characteristic of a helicopter rotor system turning at low-rotor rpm and striking the terrain. Furthermore, the damage and distress to the IFWU show that the unit had malfunctioned: the damage is not characteristic of impact damage. It is concluded, therefore, that the main rotor was not being driven at impact. The helicopter was hovering in calm air about 165feet above ground level, at a density altitude of more than 6000feet. Out-of-ground-effect manoeuvring at this density altitude at high gross weight places a large torque loading on the main-rotor transmission and driving components. At this high power setting and blade pitch angle, the loss of drive resulted in rapid decay of the main-rotor rpm, and the proximity to the ground left little room for recovery. The pilot could not regain the rpm and was unable to prevent the helicopter from descending rapidly when the lift being generated by the rotor blades was no longer sufficient to sustain flight. Jettisoning the load lightened the helicopter, allowing it to climb momentarily; it then continued to descend and struck the terrain. It was assessed that the fuel remaining at impact was sufficient for 15minutes of flight before requiring refuelling. The engine was running on the ground after impact. Because the engine was capable of producing full power during the test cell examination, vibration levels were acceptable, and the engine was operating on the ground after impact, it is concluded that the engine did not lose power during flight. The IFWU showed signs of distress related to the RHL external load type of operation, which imposed a high number of loading cycles, in the order of 30perhour. This high cycle rate accelerated the wear on the load-bearing surfaces resulting from spalling and abrasive wear. The scheduled TBO for the Lama's IFWU is not based on the number of operating cycles. Eurocopter considers time-in-service the sole parameter for determining TBO. The IFWU was subjected to a high number of loading cycles and contamination; accordingly, the IFWU, with only 1090hours since overhaul, malfunctioned before its TBO. A review of the technical records for the accident helicopter revealed that the 800-hour inspection of the IFWU was not accomplished; therefore knowledge of its structural integrity was compromised. Compliance with this inspection may reduce the risk of failure by affording an opportunity to identify anomalies and consequently return the IFWU to a Eurocopter- approved repair facility for overhaul and to clean the unit of contamination before return to service. During the freewheeling condition and repeated cyclic loading of the IFWU, the debris generated by the wear processes acted as an abrasive, causing accelerated wear of the cage/retainer, ramps, ring, and rollers. This metal debris was trapped within the assembly because of its design, contaminating the IFWU. Rapid descent and flare may cause the main rotor to accelerate, and the IFWU may disengage (or freewheel) and then re-engage. Although the composite main-rotor blades are more aerodynamically efficient than the original Eurocopter metal blades, both sets of blades can enter autorotation. The degree to which this occurs depends on flight profile, pitch angle, density altitude, and aircraft gross weight. The manner in which the helicopter was being operated is believed to have contributed to freewheeling. The IFWU would have been subjected to more frequent and severe re-engagements, accelerating the wear. The approved RFM supplement for the composite main-rotor blades supplemental type certificate was not incorporated in the accident helicopter's RFM. Further, the pitch indicator gauge was not placarded in accordance with this approved supplement. The operator may not have respected the limitation associated with the LOM blade installation. This situation may have contributed to overloading the IFWU. The input freewheel unit (IFWU) and drive shaft assembly failed. Consequently, the engine could not drive the transmission and the main-rotor blades. The combination of the loss of drive and the operating flight regime resulted in the main-rotor rpm decaying so rapidly that the pilot was unable to control the loss of rotor rpm and could not prevent the helicopter from descending and striking the terrain. The IFWU failed because of the wear on the internal parts caused by the repeated heavy lift operations and because of the contamination suspended and trapped in the lubricating oil between the unit's rotating parts. The operator did not perform the 800-hour inspection of the IFWU assembly required by the Eurocopter maintenance manual. As a result, the contamination and excessive wear of the freewheel internal parts were not detected. To arrive at the time between overhauls, operators do not calculate and account for the number of cycles experienced in operation. Eurocopter assigns a total time-in-service to the IFWU, and the same time-in-service applies regardless of the operation type. The IFWU was subjected to a high number of loading cycles and contamination, reached its design limit before 1800hours in service, and subsequently malfunctioned. The manner in which the helicopter was operated allowed freewheeling to occur during rapid descents, contributing to accelerated wear of the subcomponent parts through disengagements and successive re-engagements.Findings as to Causes and Contributing Factors The input freewheel unit (IFWU) and drive shaft assembly failed. Consequently, the engine could not drive the transmission and the main-rotor blades. The combination of the loss of drive and the operating flight regime resulted in the main-rotor rpm decaying so rapidly that the pilot was unable to control the loss of rotor rpm and could not prevent the helicopter from descending and striking the terrain. The IFWU failed because of the wear on the internal parts caused by the repeated heavy lift operations and because of the contamination suspended and trapped in the lubricating oil between the unit's rotating parts. The operator did not perform the 800-hour inspection of the IFWU assembly required by the Eurocopter maintenance manual. As a result, the contamination and excessive wear of the freewheel internal parts were not detected. To arrive at the time between overhauls, operators do not calculate and account for the number of cycles experienced in operation. Eurocopter assigns a total time-in-service to the IFWU, and the same time-in-service applies regardless of the operation type. The IFWU was subjected to a high number of loading cycles and contamination, reached its design limit before 1800hours in service, and subsequently malfunctioned. The manner in which the helicopter was operated allowed freewheeling to occur during rapid descents, contributing to accelerated wear of the subcomponent parts through disengagements and successive re-engagements. Helicopters engaged in repetitive heavy-lift (RHL) external load operations frequently experience as many as 30cycles per hour and sometimes more. The helicopter manufacturer assumed an average of six cycles per hour when designing aircraft components for the Lama and, in this RHL external load environment, underestimated maintenance schedules. The operator may not have respected the limitation associated with the LOM blade installation because the approved rotorcraft flight manual supplement for the composite main-rotor blades supplemental type certificate was not incorporated in the accident helicopter's flight manual and the pitch indicator gauge was not placarded in accordance with the approved supplement. This situation may have contributed to overloading the IFWU. Eurocopter allows the reuse and mixing of subcomponent parts during repair or at overhaul. Time-continued or on-condition components have subcomponent parts that may satisfy overhaul criteria but that have accrued time in service and cycles in operation that may jeopardize their future life expectancy or maintenance schedule. The helicopter was operated repeatedly in a hover about 165feet above ground level, placing the helicopter in the Avoid Continuous Operation section of the speed altitude envelope chart. In this area of the chart, an emergency landing is unlikely in the event of an engine power loss.Findings as to Risk Helicopters engaged in repetitive heavy-lift (RHL) external load operations frequently experience as many as 30cycles per hour and sometimes more. The helicopter manufacturer assumed an average of six cycles per hour when designing aircraft components for the Lama and, in this RHL external load environment, underestimated maintenance schedules. The operator may not have respected the limitation associated with the LOM blade installation because the approved rotorcraft flight manual supplement for the composite main-rotor blades supplemental type certificate was not incorporated in the accident helicopter's flight manual and the pitch indicator gauge was not placarded in accordance with the approved supplement. This situation may have contributed to overloading the IFWU. Eurocopter allows the reuse and mixing of subcomponent parts during repair or at overhaul. Time-continued or on-condition components have subcomponent parts that may satisfy overhaul criteria but that have accrued time in service and cycles in operation that may jeopardize their future life expectancy or maintenance schedule. The helicopter was operated repeatedly in a hover about 165feet above ground level, placing the helicopter in the Avoid Continuous Operation section of the speed altitude envelope chart. In this area of the chart, an emergency landing is unlikely in the event of an engine power loss. Eurocopter does not attribute a service life limit to the IFWU. Identification for this component takes the form of data plates or stickers that can become detached.Other Findings Eurocopter does not attribute a service life limit to the IFWU. Identification for this component takes the form of data plates or stickers that can become detached. After the examination of the second input freewheel unit (IFWU) (serialnumberC-560), the operator reduced the component inspection interval to 400hours. However, this inspection is distinct and separate from the airframe inspections because the IFWU may be installed on different helicopters with various inspection deadlines. This new inspection schedule has not been adopted by all operators of the 315B Lama helicopter. Eurocopter issued AS [sic,SA] 315BTELEX Letter No.55 (dated13February2002) to remind Lama operators of the maintenance manual's 800-hour inspection requirement for the IFWU. On 19 February 2002, the TSB issued Aviation Safety AdvisoryA020007-1, Loss of drive - Eurocopter Lama, Input Freewheel Unit to Transport Canada. The advisory stated that Transport Canada may wish to take action to ensure that the Eurocopter Lama is operated, inspected, and overhauled in a manner that takes into account the adverse effects on the IFWU of repetitive heavy-lift operations. Transport Canada published an article entitled Freewheel Units in Vortex, issue2/2002. The article is applicable to all helicopter operators because all helicopters have a mechanism to automatically disengage the dead engine from the transmission. Transport Canada may undertake further action on this issue. This report concludes the TSB's investigation into this occurrence. Consequently, the Board authorized the release of this report on 21May2003. 1.A logging cycle is the time between refuelling operations and, in this case, was usually planned for an endurance of 60 to 75 minutes, with 90 US gallons of fuel. 2.A turn refers to the two-way flight of the helicopter, usually up and down a hill, to pick up and deliver a load to the log-landing area. 3.Canadian Aviation Regulation 201.05(1) and (2). 4.On-condition or time-continued components satisfy overhaul criteria but are an amalgamation of new and used parts. This definition is not intended to contradict any authorized manual, Canadian Aviation Regulation, or Transport Canada-authorized publication. 5.Waldron and Co., Report No. 01-313. 6.Eurocopter, Examination Report No. STSA147/02. 7.Eurocopter, Investigative Report Nos. 2891, dated 06-04-1992; 2126/92, dated 30-07-1992; and 430/93, dated 29-01-1993. 8.The Eurocopter maintenance manual only considers cycles in a particular case for main-rotor blades (metal type) and defines a cycle as one landing, whether the rotor is subsequently stopped or not. For sling operation, one cycle means one load-carrying operation.Safety Action Taken After the examination of the second input freewheel unit (IFWU) (serialnumberC-560), the operator reduced the component inspection interval to 400hours. However, this inspection is distinct and separate from the airframe inspections because the IFWU may be installed on different helicopters with various inspection deadlines. This new inspection schedule has not been adopted by all operators of the 315B Lama helicopter. Eurocopter issued AS [sic,SA] 315BTELEX Letter No.55 (dated13February2002) to remind Lama operators of the maintenance manual's 800-hour inspection requirement for the IFWU. On 19 February 2002, the TSB issued Aviation Safety AdvisoryA020007-1, Loss of drive - Eurocopter Lama, Input Freewheel Unit to Transport Canada. The advisory stated that Transport Canada may wish to take action to ensure that the Eurocopter Lama is operated, inspected, and overhauled in a manner that takes into account the adverse effects on the IFWU of repetitive heavy-lift operations. Transport Canada published an article entitled Freewheel Units in Vortex, issue2/2002. The article is applicable to all helicopter operators because all helicopters have a mechanism to automatically disengage the dead engine from the transmission. Transport Canada may undertake further action on this issue. This report concludes the TSB's investigation into this occurrence. Consequently, the Board authorized the release of this report on 21May2003. 1.A logging cycle is the time between refuelling operations and, in this case, was usually planned for an endurance of 60 to 75 minutes, with 90 US gallons of fuel. 2.A turn refers to the two-way flight of the helicopter, usually up and down a hill, to pick up and deliver a load to the log-landing area. 3.Canadian Aviation Regulation 201.05(1) and (2). 4.On-condition or time-continued components satisfy overhaul criteria but are an amalgamation of new and used parts. This definition is not intended to contradict any authorized manual, Canadian Aviation Regulation, or Transport Canada-authorized publication. 5.Waldron and Co., Report No. 01-313. 6.Eurocopter, Examination Report No. STSA147/02. 7.Eurocopter, Investigative Report Nos. 2891, dated 06-04-1992; 2126/92, dated 30-07-1992; and 430/93, dated 29-01-1993. 8.The Eurocopter maintenance manual only considers cycles in a particular case for main-rotor blades (metal type) and defines a cycle as one landing, whether the rotor is subsequently stopped or not. For sling operation, one cycle means one load-carrying operation.